1. Field of the Invention
The present invention relates to a fuel cell stack including a plurality of fuel cells for generating electrical energy by electrochemical reactions of a fuel gas and an oxygen-containing gas. The fuel cells are stacked together in a stacking direction, and a pair of end plates are provided at both ends in the stacking direction.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs a polymer ion exchange membrane as an electrolyte membrane, and the polymer electrolyte membrane is interposed between an anode and a cathode to form a membrane electrode assembly (MEA). The membrane electrode assembly and a pair of separators sandwiching the membrane electrode assembly make up a power generation cell for generating electricity. In use, typically, a predetermined number of the power generation cells are stacked together to form a fuel cell stack, e.g., mounted in a vehicle.
In particular, in the case where the fuel cell stack is used for the in-vehicle application, in addition to shocks and vibrations, external loads tend to be applied to the fuel cell stack. Therefore, in an attempt to achieve a desired rigidity of the entire fuel cell stack, structure where the fuel cell stack is placed in a box has been adopted. As a type of this structure, for example, fastening structure of a fuel cell stack as disclosed in Japanese Laid-Open Patent Publication No. 2008-112708 (hereinafter referred to as the conventional technique 1) is known.
In this fastening structure, as shown in FIG. 16, end plates 2a, 2b are tightly fixed to both of upper and lower end surfaces of a separator 1. Four outer surfaces excluding both of the upper and lower end surfaces of the separator 1 are detachably covered by a pair of U-shaped enclosure panels 3a, 3b. In the detachable fastening structure, recesses formed along circumferential surfaces of side surface portions of the end plates 2a, 2b and protrusions formed on upper and lower edges of the enclosure panels 3a, 3b are fitted together.
Further, for example, an in-vehicle fuel cell stack as disclosed in Japanese Laid-Open Patent Publication No. 2001-143742 (hereinafter referred to as the conventional technique 2) is known. The fuel cell stack has a mounting structure for mounting the fuel cell stack in a vehicle. The mounting structure includes fixed support means and movable support means. The fixed support means is provided on one of end plates positioned at one end of the fuel cell stack in the stacking direction for holding one of end plates on the vehicle through a rubber mount. The movable support means is provided on the other of the end plates positioned at the other end of the fuel cell stack in the stacking direction for holding the other of the end plates through a rubber mount in a movable manner with respect to the vehicle in the stacking direction.